Relating sulfate and methane dynamics to geology: Accretionary prism offshore SW Taiwan

Pei Chuan Chuang, Andrew W. Dale, Klaus Wallmann, Matthias Haeckel, Tsanyao Frank Yang, Nai Chen Chen, Hsiao Chi Chen, Hsuan Wen Chen, Saulwood Lin, Chih Hsien Sun, Chen Feng You, Chorng Shern Horng, Yunshuen Wang, San Hsiung Chung

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

Geochemical data (CH4, SO42-, I -, Cl-, particulate organic carbon (POC), δ13C-CH4, and δ13C-CO2) are presented from the upper 30 m of marine sediment on a tectonic submarine accretionary wedge offshore southwest Taiwan. The sampling stations covered three ridges (Tai-Nan, Yung-An, and Good Weather), each characterized by bottom simulating reflectors, acoustic turbidity, and different types of faulting and anticlines. Sulfate and iodide concentrations varied little from seawater-like values in the upper 1-3 m of sediment at all stations; a feature that is consistent with irrigation of seawater by gas bubbles rising through the soft surface sediments. Below this depth, sulfate was rapidly consumed within 5-10 m by anaerobic oxidation of methane (AOM) at the sulfate-methane transition. Carbon isotopic data imply a mainly biogenic methane source. A numerical transport-reaction model was used to identify the supply pathways of methane and estimate depth-integrated turnover rates at the three ridges. Methane gas ascending from deep layers, facilitated by thrusts and faults, was by far the dominant term in the methane budget at all sites. Differences in the proximity of the sampling sites to the faults and anticlines mainly accounted for the variability in gas fluxes and depth-integrated AOM rates. By comparison, methane produced in situ by POC degradation within the modeled sediment column was unimportant. This study demonstrates that the geochemical trends in the continental margins offshore SW Taiwan are closely related to the different geological settings. Key Points Diagenetic processes are quantified by a reaction-transport model Data reveal irrigation of seawater by gas bubbles and AOM play important role Geochemical trends are closely related to the different geological settings

Original languageEnglish
Pages (from-to)2523-2545
Number of pages23
JournalGeochemistry, Geophysics, Geosystems
Volume14
Issue number7
DOIs
Publication statusPublished - 2013 Jul 1

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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